I thought amps doubled the output at 4ohm, yet there are some rated 200W @ 8ohm and 300W @ 4ohm. Why is that? If there is no 4ohm spec from the manufacturer then how does one determine the output at 4ohms?
How can the A1400-8 output the same (all channels driven) 200W at all impedances?
Is there a way or formula to determine the one,two, or three channel driven output based soley on the all channels driven rating? For example, if a 5 channel amp is rated 200W all channels driven then what would be a reasonable estimate for 1,2,and 3 channels driven?
There is no magic 'formula' unless you know exactly how the amp structure is made up. Most amps will only drive one channel to it's max output 200W @ 8ohm for example and that channel would then be able to have a 50% increase in power when a drop to 4 ohms is introduced giving you 300W, this is about as close to a formula as you will get. The A1400 is able to deliver no matter what resistance due to it's design. It is able to feed any amount of power required to a single channel upto it's max output of ~1400W if need be.
